Method of producing heat sealable filter paper for making infusion packages



Mar h 24, 1959 2 879,172

. A. SORG METHOD OF PRODUCING HEAT SEALABLE FILTER PAPER FOR MAKING INFUSION PACKAGES Filed March- 11, 1957 v 5 Sheets-$heet 1 u 1 ."Z n T Y INVENTOR ATTORNEY March 24, 1959 i ,'5o 2,879,172 METHOD OF PRODUCING HEAT SEALABLE FILTER PAPER FOR MAKING INFUSION PACKAGES Filed March 11, 1957 0000, 1 0 0 0 0 0 hohofio All . INVENTOR Han/v1; 5026.

'5 Sheets-Sheet 2 AT-TORNEY March 24, 1959 A S R' 2,879,172

METHOD OF PRODUCING i-IEAT 'SEALABLE FILTERIPAPER FOR MAKING INFUSION PACKAGES Filed March 11, 1957 Sheets-Sheet 3 METHOD OF PRODUCING HEAT SEALABLE FILTER PAPER FOR MAKING INFUSION PACKAGES Adam Srg,'Glendale, N.Y., assignor, by mesne assign ments, to Adam Sorg and Edwin V. Hadley, New York, NY.

Application March 11, 1957, Serial No. 645,094

11 Claims. (Cl. 117--11) This invention relates to improvements in the art of producing a comparatively high wet strength filter paper carrying a continuouspattern formed of lines or dots and/or combinations thereof of a tasteless and odorless thermoplastic, a thermo-setting, or a thermo-responsive resin, and having infusion areas therein.

This application is a continuation-in-part of my application Serial No. 420,317, now abandoned, filed April 1, 1954.

Another object of the invention is the provision of a comparatively high wet strength filter paper carrying on at least one surface there-of a superimposed pattern of a predetermined design, said .pattern being delineated in accordance with said design with a thermo-respo-nsive plastic resin, leaving infusion areas between said dolineations, and the provision of means to restore any infusion areas between saiddelineations which have been reduced by capillary action between the fibrous constituents of the paper and .said resin.

A further object of the invention is the step of moving the paper strip, after the pattern has been applied and heated, over at least one comparatively sharp edge to break up any delineations so as to produce infusion areas therein in addition to the infusion areas between said delineations.

Yet another object of the invention is the provision of a method of producing a comparativeiy high wet strength filter paper in strip form and having a coating comprising a merino-responsive plastic resin on one face thereof; and having infusion areas interspersed through out .said coating and formed by breaking the coated surface thereof by passing the coated paper through a tunnel or the like to raise its temperature, and passing the paper out of the tunnel and over and under a series of comparatively sharp mechanical corners to subject the coated paper to a series of momentary obverse and reverse strains.

Other objects and advantages of the invention will be apparent to those skilled in the art upon a study of this specification and the accompanying drawings.

Referring to the drawings which are diagrammatic, and which are given by Way of example to illustrate the invention:

Figure 1 is a diagrammatic representation of'apparatus for producing my new and improved heat scalable filter P p Figure 2 is a diagram similar to Figure l for producing a coated heat scalable filter paper;

Figure 3 is a fragmentary view of a further modification of the arrangements shown in Figs. 1 and 2;

Figure 4 is an enlarged cross sectional'view of a piece of filter paper coated with a thermo-responsive resin; 9 Figure 5 is a cross sectional view of the coated sheet of Figure 4 after the same has been broken by heating and passing it over one or more comparatively sharp mechanical corners thereby subjecting .the'paper to obverse and reverse strains;

Figure -6 is a magnified cross sectional view of .a web identically the same doctor blade 19. roller 46 cooperates with the roller 45 in a manner similar .to the cooperation between the rollers 14 and 15 of filter paper imprinted or coated withthermo-responsive plastic resin being passed .over a comparatively sharp mechanical corner;

Figures 7, 8 and 9 are enlarged fragmentary views of superimposiugs of the plastic on the surface of the paper showing an open circle pattern, a curved line pattern and a broken line pattern respectively; and

Figure 10 is a diagrammatic representation of an extruding system for extruding polyethylene and other thermoplastics directly on to a filter sheet and thereafter breaking the film in accordance with the invention.

Referring first to Figure 1, a roll 10 of comparatively high wet strength filter 'paper is supported for rotation on a shaft 11 and the paper web 12 is led from this roll over a roller 13 and then under a second roller 14 which exerts pressure upon an embossed roller 15 which is rotated on its shaft 16 bythe paper web 12 passing between the rollers 1e and 16. The roller 15 is etched, engraved or otherwise provided with a pattern or a predetermined design. It rotates with its lower portion submerged in a solution of thermo-responsive resin contained in a vesselli in which the liquid level is preferably maintained substantially constant.

A support 18 spaced apart from the roller 15 carries a-doctor blade '19 for removing surplus resin and insuring the uniformity of the resin imparted tothe paper. As the paper web 12 passes between the rollers 14 and 15, its under .surface (the surface which was in contact with the roll 15) is printed or otherwise has impressed thereon a pattern of the resin in the wanted design and this pattern is delineated with 'the'resin, and betweenthe lines are infusion areas through which liquid may pass when the article is submerged. As the paper web 12 leaves the rollers '14 and '15, it'p'a'sses over rollers '20, 21 and 22 and is thereby moved upwardly and its direction is .changed so that it moves upwardly to a higher level and enters the mouth 23 of a heating and drying chamber 25 which may be heated, for example, by means of a steam coil 26 and to further facilitate the drying, a

lower 27, for example, of the sirocco type draws 'air from .the chamber '25 so that it may be replaced'by air warmed by the steam pipes 26. The exhausted air passes through the conduit 28 and to the center or inlet 2h of the blower 27 and the air is discharged therefrom through the opening30.

The paper web 12 leaves the chamber 25 in a warm condition via the exit 24 and passes over a roller .31 and then over the upper surface of a rectangular member 32a, and thence over a comparative sharp mechanical corner to a drying roller 35, over asecond drying roller .36 and then it is formed into a roll 37 on the shaft 38.

As the warmed paper passes over the substantially square mechanical corner, the areas which are covered with the plastic, dueto the embossing thereof, are broken up so that they are interspersed with small infusion areas which together with the .infusionareas in the spaces between the delineations, gives increased infusion areas.

As the paper traverses the rollers 35 and 3.6, substantiailly all of the residual solvent is dried out of the impressed pattern and the filter paper is ready to be made iuto'infusion packages by forming thepackage about a given quantity ofinfusionmaterial and sealing the edges together by heat sealing, orthepackagesmay be made up, filled and sealed byany other desired method.

iReferring tnow'to Figure '2, the apparatus is substantially the same as that shown in Figure 1 except that in place or :the embossed roller 15, .1 provide a coating roller 45., which is carried on the :shaft 16 andhaving In FigureZ, a

described above, and the web 12 is coated with the plastic instead of being imprinted with it.

In both instances, the paper web 12 is passed through the heating and drying chamber 25 and as it leaves this chamber at an elevated temperature, it passes under and over and again under the rectangular members 32, 33 and 34, respectively, and is broken to provide increased infusion areas in the paper.

In this instance, however, the paper encounters mechanical corners 39 and 40 of member 32, then corners 41 and 42 of member 33, and then the paper encounters and traverses corners 43 and 44 of the member 34. This repetitive flexing of the paper and, at the same time, carrying it over mechanical corners effects a most complete breaking" of the plastic coating, with the result that the infusion is far superior to any other type of sealing coated paper.

This method is believed to be superior to any coating pores 49 and makes them substantially impervious to infusion fluids.

After the tissue web 12 has been broken by traversing the array of rectangular members 32, 33, 34, the coating 48 has been broken up into a series of minute areas of the plastic with spaces interspersed therein and between which are defined the pores 49 as shown in Figure 5.

In the modification shown in Figure 3, which modification merely relates to a different arrengement of the embossed or coating roller within the tank, a tank 50 has a shaft 51 which carries the embossed or coating roller 52, and cooperating therewith is a roller 53 carried on the shaft 54 which insures the bringing up of a constant thickness of the plastic from the body of plastic 55, by the roller 52.

The paper web 12 passes under spaced apart rollers 56 and 57 and is in contact with the roller 52 within a comparatively small area 58, wherein the imprinting or the coating is effected, depending upon whether the roller 52 is an embossed roller or a coating roller. The process thereafter is preferably the same as shown in Figures 1 and 2.

In Figure 6, the paper web is shown as greatly magnified as well as is the mechanical corner 39a. The paper web is represented as having pores 49 and solid sections 47 therebetween. The paper web 12 is coated' or imprinted with the plastic material 48 and it bridges over the pores 49 in the paper and thus the pores are closed. The paper web with the plastic thereon is preferably heated in an oven such as the drying chamber shown in Figure 1 or Figure 2 and as it passes along the upper surface of the member 320, it suddenly encounters a comparatively sharp corner and its direction of movement is suddenly changed to a path which is practically 90 with respect to its original path with the result, due to the fact that the plastic is on the outer surface, it is stretched greater than the paper per se and therefore the plastic breaks, and since it is supported by solid portion 47 of the paper, the breaks occur where the plastic bridges over the pores of the paper thereby leaving the paper pervious and permeable to infusion fluids.

I have found that when the plastic is imprinted on the surface of the paper, and the prints are delineations,

the surfaces of the latter break and increase the infusion areas on the paper. When the paper is coated with the plastic in an all-over coating, my process breaks this all-over coat into multitudinous infusion areas and the infusion, for instance, where such paper is made into teabags, is free and only takes a fraction of a second longer than paper which has been imprinted with the plastic.

It will be understood that hereinabove the term delineations does not necessarily means straight lines as I have produced and now have delineations in other forms as open circles, open hexagonal patterns and numerous designs involving curved and broken lines. Some of the examples of said patterns and designs are shown in Figures 7, 8 and 9.

In Figure 7, the sheet 12a has an all-over pattern formed of a series of open circles 60. In Figure 8, the sheet 12b has impressed thereon an all-over pattern comprised of curved lines 61, while in Figure 9, the sheet carries an all-over pattern of broken lines 62, 63 in which the lines 62 are angular with respect to the lines.

63 and the use ofbroken lines in substantially'the same pattern provides greater infusion areas which, of course, are increased as the lines forming the pattern are broken as described hereinabove.

The operations described above have been in connection with thermoplastic materials which are dissolved in a solvent such as acetone and applied to the surface of the paper either as an all-over coating or as an allover pattern and after the plastic material has been applied and the solvent has been driven olf then the remaining film is produced in the manner described hereinabove.

Now, other thermoplastic materials can be used. Some examples of these are vinyl chloride acetatescopolymers, vinyl acetates, and polyethylene and other odorless and tasteless plastic materials which will heat seal at temperatures in the neighborhood of to temperature.

Referring now to Figure 10, which is a diagrammatic representation of apparatus for extruding thermoplastic, such as polyethylene film onto a web of filter paper so that the thermoplastic can be used for heat sealing in making up tea bags and other infusion packages, however, before such filter paper-thermoplastic combination can be used for infusion purposes the plastic must be broken so that the infusion liquids can pass through the filter paper.

Now referring more specifically to Fig. 10, an extruding head 93 comprises a body 94 having double walled sides 95 and 96 having electrical heating elements (not shown) therein. The sides 95 and 96 are preferably formed integral with end walls 97 and 98. A removable top 100 has a dome 99 which may carry additional heat elements (not shown). The dome is held onto the body by matching flanges 101, 102 on the body and on the dome, respectively, with a sealing gasket therebetween by suitable screws (not shown).

The extruder has a bottom wall 103 carrying an extension which is hollow inside, and communicating with the hollow and within a nozzle 106 is an elongated slot 104 that communicates with the interior of the extruder through said hollow. Spiral conveyor means (not shown) is provided in the extruder for impressing suitable pressures moving the thermoplastic material within the lower portion of the extruder body and forcing said material through the elongated slot 104 to form a thin thermoplastic film and deposit it onto a moving paper web designated by the numeral 74. One or more heating elements 107 may be mounted on the outer walls of the extruder and they may also be thermostatically controlled.

The web 74 is led from a reel 72 of filter paper which is supported for rotation on a shaft 73.

The web 74 passes over a roller 108 so that its surface is closely adjacent to the nozzle 106. The web 74 then passes between the roller 108 and a chilling roller 109 so that the thermoplastic web extruded onto the web 74 is chilled'. The web '74 then passes over the up er surface of a rectangular member 32a and over a can paratively sharp mechanical corner 110 and thencedownwardly to a second sharp corner 111-on a second rectangular member 112. After the combined websleave the rectangular member 112 they pass between rollers 113 and 114 and thence to a takeup reel 115 which is carried on a shaft 116. The rollers '113 and 114 are carried respectively on shafts 117 and 118 while the rollers 106 and 109 are respectively carried on shafts 119 and 120. in this last mentioned instance the polyethylene film is extruded directly onto the filter paper web and the drying operations shown in Figs. 1 and 2 are not necessary in view of the fact that the polyethylene film carries nosolvent as does the viuylcompounds.

The plastic web orxfilrn which is extruded onto the filter paper web 74 is broken during itstransit over the sharp corners 110 and 111 of the rectangular members 320: and 112. It will be noted that as the combined web passes over the rectangular rnember 32a, the; plastic film is on the outside and the action is like that shown in the enlarged view,Fig. 6, 'while when the combined web passes around the corner 111 of Fig. 10, the plastic film is on the inside and the paper web is on the outside so in one operation the double stretch is effected, and I have found that at one pass this effects the breaking of the plastic film to the extent that rapid infusion is effected.

In the above description I have referred to vinyl resins which are in solution with a thinner such as acetone. However, there are several which I might specifically mention as particularly suitable for heat sealing purposes. One is vinyl chloride acetate and another is vinyl acetate copolymer.

Now, in connection with the paper webs upon which the polyethylene is extruded these are also breakable to even a greater extent than the vinyl resins because of the fact that the polyethylene doesnt contain any solvent or thinner. Where polyethylene is used one great advantage is that there is no necessity of having to drive off a solvent, since no solvent is used with polyethylene. Another advantage is that polyethylene heat seals at a much lower temperature than does the vinyl resins. For example, the vinyl resins heat seal at temperatures in the neighborhood of 400-450 F. while the polyethylene heat seals at temperatures of the order of 250-300 F.

Although I have mentioned hereinabove several heat sealing resins it will be understood that I may employ other thermoplastic resins which are substantially odorless and tasteless and which may be heat sealed .at temperatures within the range of 250-450" F.

Having described the invention in detail and having given by way of example thermoplastic resins of both the type which are in solution with a thinner and the type which may be extruded onto a filter paper web it will be understood that I am not to be limited to the exact materials described, as many changes may be made in the arrangement shown and described within the scope of the following claims.

What is claimed is:

1. The method of producing a heat sealable paper for making infusion packages, which comprises the step of delineating an all-over pattern of a solution of a thermoresponsive vinyl resin on a surface of a strip of filter paper, thereby providing infusion areas between the delineations, the step of drying said resin thereon, and the final step of causing consecutive increments of said surfaces bearing said delineations and the delineations thereon to stretch more than the opposite surfaces thereof and thereby breaking up portions of the delineations of said pattern to form additional infusion areas therein.

2. The method of producing a heat sealable paper for making infusion packages, comprising the step of applying a pattern of a thermo-responsive vinyl resin as a solution on one surface of a strip of filter paper, the step of drying out solvent from the resin on said paper by passing the same through a heated drying chamber, "and the final step of passing said paper, while it is still warm, over a comparatively sharp mechanical corner for breaking the surfaces of portions of lines forming said pattern to render substantial portions thereof pervious' to a liquid used in making an infusion.

3. The method of producing a heat sealable paper for making infusion packages comprising the step of applying a coating of'a thermo-plastic resin which is substantially odorless, tasteless, and which may be used for heat sealing at a temperature lying between 250" F. and 450 F. on one surface of a strip of tissue paper, the step of drying out solvent from the resin on said paper by passing the same through a heated drying chamber, the final step of stretching said plastic resin to a least a greater extent than the surface of the paper bearing'it and thereby causing (the .plastic resin to uncover pores in said paper by breaking, thereby rendering substantial portions of said .patternpervious to a liquid used in making an infusion.

4. The method of producing a heat sealable paper for making. infusion packages, comprising the step of applying a coating of a solution of thermoplastic resin whichis substantially odorless, tasteless, and which may .be used for heat sealing at a temperaturelying between 250 F. and 450 F. on onesurface of a. strip of filter paper, the step of drying out solvent from the resin on said paper by passing the same through a heated drying chamber, the final step of streching said plastic resin to at least a greater extent than the surface of the paper hearing it and thereby causing the plastic resin to uncover pores in said paper by breaking, thereby rendering substantial portions of said coating permeable to a liquid used in making an infusion.

5. The method of producing a heat sealable paper for making infusion packages, which comprises the step of delineating an all-over pattern of a solution of a thermoplastic resin which is substantially odorless, tasteless, and which may be used for heat sealing at a temperature lying between 250 F. and 450 F. on a surface of a strip of filter paper, thereby providing infusion areas between the delineations, the step of drying said resin thereon, and the final step of passing the paper and the dried resin thereon over a comparatively sharp corner, thereby breaking portions of the delineations of said pattern to uncover additional infusion areas in said paper.

6. The method of producing a heat sealable paper for making infusion packages, which comprises, the step of delineating an all-over pattern of a solution of a thermoplastic resin which is substantially odorless, tasteless, and which may be used for heat sealing at a temperature lying between 250 F. and 450 F. on a surface of a strip of filter paper, thereby providing infusison areas between the delineations, the step of drying said resin thereon, and the final step of passing the paper bearing said pattern over a series of compaartively sharp corners, and subjecting the embossed paper to a series of momentary obverse and reverse strains and breaking portions of the surfaces of the plastic resin to open up some of the pores which were covered by the plastic resin.

7. The method of producing a heat sealable paper for making infusion packages, which comprises, the step of applying a coating of a solution of a thermoplastic resin which is substantially odorless, tasteless, and which may be used for heat sealing at a temperature lying between 250 F. and 450 F. on a surface of a strip of filter paper, the step of drying said resin thereon, and the final step of causing consecutive increments of said surface to stretch more than the opposite surfaces thereof and thereby breaking up said coating to form infusion areas therein.

8. The method of producing a heat sealable paper for making infusion packages, which comprises, the step of delineating an all-over pattern of a solution of a thermoplastic resin which is substantially odorless, tasteless, and which may be used for heat sealing at a temperature lying between 250 F. and, 450 F. onv asurface of ,a stripof filter paper, thereby providing infusion areas. between the delineations, thefstep of drying said resin thereon, and the final step of passing said strip over a series'of comparatively sharp corners in a festooned array so as to subject the strip to a series of momentary obverse and reverse strains thereby breaking up said coating to form infusion areas therein.

9. The method of producing a heat seaiable paper for making infusion packages, comprising, the step of applying a pattern of a solution of a thermoplastic resin which is substantially odorless, tasteless, and which may be used for heat sealing at a temperature lying between 250 F. and 450 F. on one surface of a strip of tissue paper, said pattern comprising an array of open circles, the step of drying out solvent from the resin on said paper by passing the same through aheated drying chamber, and the final step of-passing said paper over at least one comparatively sharp mechanical corner for breaking the surfaces of per tions of arcuate lines forming said pattern to render substantial portions thereof pervious to a liquid used in making an infusion.

10. The method of producing a heat scalable paper for making infusion packages, comprising, the step of applying a pattern of a solution of a thermoplastic resin which is substantially odorless, tasteless, and which may be used for heat sealing at a temperature lying between 250 F.

and 450, F, on one surface of a strip of tissue paper,.said pattern comprising an array of curved lines, the step of drying outsolvent from the resin on said paper by passing the same through a heated drying chamber, and the final step of passing said paper over at least one comparatively jsharp mechanical corner for breaking the surfaces of portions of lines forming said pattern torender substantial portions thereof pervious to a liquid used in making an infusion.

p 11. The method of producing a heat scalable papcrrfor making infusion packages, comprising, the step of applying a film of thermoplastic resin which is substantially odorless, tasteless, and which may be used for heat seal ing at a temperature lying between 250 F. and 450 F. on one surface of a strip'of tissue paper, and the final step of passingfsaid paper .over at least one comparatively sharp mechanical corner for breaking said film and thereby rendering substantial portions of said film pervious to a liquid used in making aninfusion; 1

j j References Citedin the tile of this patent UNITED STATES, PATENTS i 1,185,600 Holt May 30, 1916 Hofierbert July 28, I942 

1. THE METHOD OF PRODUCING A HEAT SEALABLE PAPER FOR MAKING INFUSION PACKAGES, WHICH COMPRISES THE STEP OF DELINEATING AN ALL-OVER PATTERN OF A SOLUTION OF A THERMORESPONSIVE VINYL RESIN ON A SURFACE OF A STRIP OF FILTER PAPER, THEREBY PROVIDING INFUSION AREAS BETWEEN THE DELINEATIONS, THE STEP OF DRYING SAID RESIN THEREON, AND THE FINAL STEP OF CASING CONSECUTIVE INCREMENTS OF SAID SURFACES BEARING SAID DELINEATIONS AND THE DELINEATIONS THEREON TO STRETCH MORE THAN THE OPPOSITE SURFACES THEREOF AND THEREBY BREAKING UP PORTIONS OF THE DELINEATIONS OF SAID PATTERN TO FORM ADDITIONAL INFUSTION AREAS THEREIN. 